Diseases of the Liver 



95 



to this disease. In certain portions of this country where 

 once turkey raising was a promising industry it has practi- 

 cally vanished because of this disease. The disease is not 

 usually as fatal to adult chickens but may cause very serious 

 losses at times. It is believed by several prominent investi- 

 gators of this disease that white diarrhea, so destructive to 

 young chicks, is caused by the same organism as blackliead. 

 (For further discussion of this see Chapter XVIII.) 



The cause of blackhead disease according to Theobald 

 Smith ^ is a minute par- 

 asitic protozo5n known as 

 Amoeba meleagr idis. 

 These appear as minute 

 round bodies not more 

 than 10 microns (25V0 

 inch) in diameter em- 

 bedded in the submucous 

 and intramuscular tissue 

 of the wall of the ceca 

 and may extend even be- 

 yond these to the mesen- 

 teries. In the liver there 

 are circular spots (Fig. 

 9) representing partial 

 necrosis of the liver tissue and in these spots the same or- 

 ganisms are also present in great numbers. The analogy 

 between this organism and that concerned in human amoe- 

 biasis is very close. 



More recently Cole and Hadley " at the Rhode Island 



Fig. 9. — Showing condition of liver in 

 "blackhead." (Modified after Moore.) 



1 Smith, Theobald., "An Infectious Disease among Turkeys 

 Caused by Protozoa (Infectious enterohepatitis)." U. S. Dept. 

 of Agr., Bur. Anim. Ind., Bui. 8, pp. 7-38, 1895. 



- Cole, L. J., and Hadley, P. B., "Blackhead in Turkeys." Rhode 

 Island Expt. Stat. Bui. No. 141, pp. 138-272, 1910. 



